SEQUENTIAL CIRCUITS Sequential Circuits 1 Two Types of

SEQUENTIAL CIRCUITS Sequential Circuits 1

Two Types of Switching Circuits • Combinational Circuits – Combinational circuits have only input and output. Output depends on input. – Example: AND, OR, NAND, NOR, XOR etc • Sequential Circuits – Sequential circuits have input, present state, next state and output. Next state depends upon present state and input. Output depends upon present state and input – Example: Flip-Flops etc Sequential Circuits 2

FLIP FLOPS AND THEIR APPLICATIONS 1. Sequential Circuits 3

Sequential Circuits 4

Sequential Circuits 5

Sequential Circuits 6

Sequential Circuits 7

Sequential Circuits 8

When S = 1, Q+ = 1 When R = 1, Q+ = 0 When T = 1, State changes When any two out of S, R, T equals 1, we have don’t care Sequential Circuits 9

Sequential Circuits 10

Example 1: Design a modulo-8 binary -up counter using T- Flip Flop Modulo 8 counter : Counts upto 7. So we need three Flip-flops for eight states Sequential Circuits 11

modulo-8 counter Sequential Circuits 12

modulo-8 counter Sequential Circuits 13

modulo-8 counter Sequential Circuits 14

modulo-8 counter Sequential Circuits 15

Example 2: Design a modulo-8 binary -up counter using T- Flip Flop with input x Modulo 8 counter : Counts upto 7. So we need three Flip-flops for eight states Sequential Circuits 16

modulo 8 counter with I/p x Sequential Circuits 17

modulo 8 counter with I/p x Sequential Circuits 18

modulo 8 counter with I/p x Sequential Circuits 19

modulo 8 counter with I/p x Sequential Circuits 20

Example 3: Design a binary decade counter using SR- Flip Flop without input x Decade Counter: Counts up to 9. So we need four Flip-Flops for ten states Sequential Circuits 21

Binary Decade counter Sequential Circuits 22

Binary Decade counter Sequential Circuits 23

Binary Decade counter Sequential Circuits 24

Binary Decade counter Sequential Circuits 25

Binary Decade counter Sequential Circuits 26

Example 4: Design a modulo-8 counter which counts in the way specified below, use J-K Flip-Flop. Sequential Circuits 27

TRUTH TABLE: present state next state Sequential Circuits 28

Gray code counter Y 3 Sequential Circuits 29

Gray code counter: Y 2 Sequential Circuits 30

Gray code counter: Y 1 Sequential Circuits 31

Example 5: Design a T-Flip-Flop using S-R Flip-Flop Sol: Sequential Circuits 32

T Flip flop using S-R flipflop Sequential Circuits 33

Example 6: Design a J-K Flip Flop using S-R Flip Flop Sol: Sequential Circuits 34

J-K Flip Flop using S-R Flip Flop Sequential Circuits 35

Example 7: Design a sequential circuit given below using J-K Flip. Flop Sequential Circuits 36

Truth Table: I/p Present st. Next state Sequential Circuits o/p 37

Design of Seq. Circuit Sequential Circuits 38

Design of Seq. Circuit Sequential Circuits 39

Design of Seq. Circuit Sequential Circuits 40

Design of Seq. Circuit Sequential Circuits 41

Example 8: Design a binary modulo-5 counter using SRT- Flip Flop with input x Modulo-5 Counter: Counts up to 4. So we need three Flip. Flops for five states Sequential Circuits 42

Binary Modulo-5 counter STATE TABLE Sequential Circuits 43

Binary Modulo-5 counter Sequential Circuits 44

Binary Modulo-5 counter Sequential Circuits 45

Binary modulo-5 counter Note: Here S’and C’ stands for the compliment value of the corresponding cells in the S and C K-maps Assume T’ = So S’ and C’ comes out to be Sequential Circuits 46

Binary Modulo-5 counter Sequential Circuits 47

Binary modulo-5 counter Assume T’ = So S’ and C’ comes out to be Sequential Circuits 48

Binary modulo-5 counter Sequential Circuits 49

Binary modulo-5 counter Assume T’ = 1 So S’ and C’ comes out to be 0 and 0 Sequential Circuits 50

G=0 G=1 Sequential Circuits Q+ does not respond Q+ responds 51

T-G Flip Flop Application Equation This is the Application Equation of the T-G Flip-Flop Sequential Circuits 52

Example 9: Design T 2 and G 2 for a modulo 5 binary up counter Modulo-5 counter: Counts up to 4. So we need three Flip. Flops for five states Sequential Circuits 53

Modulo 5 binary upcounter STATE TABLE Sequential Circuits 54

Modulo 5 binary upcounter Sequential Circuits 55

Modulo 5 binary upcounter Sequential Circuits 56

Modulo 5 binary upcounter Sequential Circuits 57

Modulo 5 binary upcounter Sequential Circuits 58

Example 10: Design an Octal upcounter(Binary counter) using S-C Flip-Flop using Tabular Method Octal up counter: Counts up to 7. So we need three Flip. Flops for seven states Sequential Circuits 59

Octal up counter STATE TABLE Sequential Circuits 60

Octal up counter Sequential Circuits 61

Octal up counter Sequential Circuits 62

Octal up counter Sequential Circuits 63

RULES TO DERIVE EXCITATION FUNCTION • T- Flip-Flop Sequential Circuits 64

• S-C Flip Flop Sequential Circuits 65

• J-K Flip Flop Sequential Circuits 66

• T-G Flip Flop Sequential Circuits 67

• S-C-T Flip Flop Sequential Circuits 68

Summary of Rules for all Flip-Flops Sequential Circuits 69

MODIFIED RULES FOR THE FLIP-FLOPS Sequential Circuits 70

questions ? ? ? Sequential Circuits 71